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Integrated Micro Flow Synthesis Based on Sequential Br–Li Exchange Reactions of p‐, m‐, and o‐Dibromobenzenes
Authors:Aiichiro Nagaki Dr.  Yutaka Tomida  Hirotsugu Usutani  Heejin Kim  Naofumi Takabayashi  Toshiki Nokami Dr.  Hideho Okamoto Dr.  Jun‐ichi Yoshida Prof. Dr.
Affiliation:Department of Synthetic and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo‐ku, Kyoto, 615‐8510, Japan, Fax: (+81)?75‐383‐2727
Abstract:A micro flow system consisting of micromixers and microtube reactors provides an effective method for the introduction of two electrophiles onto p‐, m‐, and o‐dibromobenzenes. The Br–Li exchange reaction of p‐dibromobenzene with nBuLi can be conducted by using the micro flow system at 20 °C, although much lower temperatures (p‐bromophenyllithium was allowed to react with an electrophile in the micro flow system at 20 °C. The p‐substituted bromobenzene thus obtained was subjected to a second Br–Li exchange reaction followed by reaction with a second electrophile at 20 °C in one flow. A similar transformation can be carried out with m‐dibromobenzene by using the micro flow system. However, the Br–Li exchange reaction of o‐dibromobenzene followed by reaction with an electrophile should be conducted at ?78 °C to avoid benzyne formation. The second Br–Li exchange reaction followed by reaction with an electrophile can be carried out at 0 °C. By using the present method, a variety of p‐, m‐, and o‐disubstituted benzenes were synthesized in one flow at much higher temperatures than are required for conventional batch reactions.
Keywords:arenes  flow reactions  integrated micro flow synthesis  lithiation  microreactors
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